This invention relates to electronic data processing units, and more particularly, to apparatus and methods for cooling a data processing unit.
Some known data processing units include multiple circuit boards configured to process and/or transmit electrical signals. Such known data processing units can include, for example, routers, switches, servers, storage devices, and/or components included within a core switch fabric of a data center. Such known data processing units include cooling systems configured to prevent overheating of the electronic circuits (e.g., the modules) included on the circuit boards contained therein. Some known cooling systems are configured to convey cooling air across the surface of the circuit boards in a single direction (e.g., from a first side to a second side). In such an arrangement, however, the electronic circuits disposed on or adjacent the second side of the circuit board are exposed to cooling air that has been heated as a result of flowing across the electronic circuits disposed on or adjacent the first side of the circuit board. Similarly stated, with such cooling systems, the electronic circuits located downstream receive cooling air having a higher temperature than that of the cooling air received by the electronic circuits located upstream.
Some known data processing units use an orthogonal midplane configuration, in which a first set of circuit boards (e.g., line cards) is coupled to the front side of a midplane in a vertical configuration and a second set of circuit boards (e.g., line cards) is coupled to the rear side of the midplane in a horizontal configuration. The orthogonal midplane configuration allows each line card from the first (i.e., front) set of line cards to be directly connected to each line card from the second (i.e., rear) set of line cards, thus eliminating the use of printed circuit board signal traces on the midplane to convey the signals between the cards. The cooling systems of known data processing units having an orthogonal midplane configuration often cool the rear set of line cards by diverting air flow from cooling channels in the front part of the chassis that are used to cool the front set of line cards. This arrangement, however, limits the degree to which the rear set of line cards can be cooled independently from the front set of line cards. Additionally, this arrangement can result in the cooling air supplied to the rear set of line cards having a higher temperature than the cooling air supplied to the front set of line cards.
Thus, a need exists for improved apparatus and methods for cooling the components (e.g., the line cards) within a data processing unit having an orthogonal midplane configuration.